Its true
There have been a few instances of a group of dwarves 4-5 strong that could successfully complete just about all the areas that NCE encompasses, having other random PCs with them along for the ride.
Being inclusive of others is more important (to me at least) than thinking in terms of party composition affecting xp gains.
My NCE character is a smidge to go for level 6. Was created last Friday, so one week. He is capped of some sort, but he verbiage is lost on me since it changed.
I feel the progression is fine. If anything, what is important to me is to get to 5 on this server, as long as that is something accomplished in a week or two then fair enough.
My real concern is my level 17, who has been 17 for a year lol. I don't dungeon very much with her, but I would like rp to sustain a FAIRLY consistent progress, at least see a message go up a quarter or so.
Following NCE I plan on being much more active and dynamic/faction type play so maybe that will kick in some progress again for her. Or maybe I will gain a fancy for slaying demons again.